Animal experiments have explored the structural and functional alterations of the afferent visual pathways in amblyopia and have emphasized the extraordinary sensitivity of the immature visual system to abnormal visual stimulation. The practical consequences of these experiments are obvious: early diagnosis of amblyopia and energetic occlusion therapy as early in life as possible. At the same time, measures must be taken to prevent visual deprivation amblyopia in the occluded eye. After successful treatment, alternating penalization with two pairs of spectacles is recommended. Pleoptics involves an enormous commitment in terms of time, personnel and costs. In view of the fact that the superiority of this treatment over occlusion therapy has yet to be proven, the current value of pleoptics appears dubious. Moreover, overtreated patients may end up with intractable diplopia. Diverging opinions exist with regard to the use of penalization as a primary treatment of amblyopia. We employ it only in special cases as an alternative to occlusion therapy. Visual deprivation in infancy caused by opacities of the ocular media, especially when they occur unilaterally, must be eliminated, and deprivation amblyopia must be treated without delay to regain useful vision. Brief periods of bilateral occlusion are recommended to avoid the highly amblyopiogenic imbalance between binocular afferent visual input. Future developments will hopefully include new objective methods to diagnose amblyopia in preverbal children and infants. The application of positron emission tomography is perhaps the first step in the direction of searching for new approaches to this problem.(ABSTRACT TRUNCATED AT 250 WORDS)